Aromatic amines are important industrial chemicals. They can be used to produce a very important class of industrial compounds such as azo dyes. Aromatic amines can be produced by chemical reduction of nitro compounds with a metal and acid such as, for example, iron or tin and hydrochloric acid or by catalytic hydrogenation using molecular hydrogen and a hydrogenation catalyst such as nickel or platinum. Nitro compounds can be readily made by direct nitration of aromatic compounds.
The product mixture produced by catalytic hydrogenation of an aromatic nitro compound generally comprises the desired amine, a corresponding phenolic compound, and unreacted aromatic nitro compound. These by-products, because of their color and deleterious effects on product properties, are undesirable and are difficult to separate from the amines by distillation. Therefore, there is an increasing need for the reduction of impurities to increase the amine purity.